Here's why:
* No experiment can be perfect: Every experiment has limitations and uncertainties. Even if countless experiments support a law, there's always a theoretical possibility of a future experiment contradicting it.
* The first law of thermodynamics is a fundamental principle: It's based on the conservation of energy, a concept that has been repeatedly verified through countless experiments and observations. While it's theoretically possible that it could be wrong, it's highly unlikely given the vast amount of evidence supporting it.
* It's a theoretical framework: The first law of thermodynamics is a model that describes the behavior of energy in the universe. Models are always simplified representations of reality, and their accuracy is constantly being refined.
Instead of "proving," science has verified the first law of thermodynamics through countless experiments and observations. No experiment has ever convincingly contradicted it.
Therefore, the first law of thermodynamics is considered a highly validated principle in science, not a "proven" one. It's a powerful tool that helps us understand the universe, and we continue to refine our understanding of it through ongoing research and experiments.
